To me, like Andy44 said, a type of lens flare effect would add to the immersion. Why? I can't look near or at the sun on a clear day without being dazzled, and in space it wouldn't be different. Since the monitors lack the dynamic range of the real world, this is one way to imitate that effect.
Maybe not having a lens flare par se, but the kind you have in FS9, where the view gets washed out the closer the sun gets to the center of the screen? And to comply with the different preferences of the users, make it optional.
You're describing Sun glare, not lens flare. DaveS already covered this above. It was originally tried in 2006 version but was removed with P1 due to it being buggy.
Have seen lens flare tried in a couple flight sims. Adds a little to the realism in most games, but I usually disable it since I don't feel it's worth the framerate hit.
@Hielor - Now, remember, the minimum is 15 pieces of lens flair. If you want to go around with just the minimum, that's fine, but you should really express yourself...